Abstract: Compressor testing facility is one of the fundamental and imperative experimental apparatus when carrying out experiments to investigate phenomena occurring within the compres-sor.In this paper,experiments have been carried out on the complex transonic compressor tes-ting facility in Beihang University to analyze the influence of the systematic Helmholtz harmonic frequency on this specific testing facility.Several modifications have been made to this compres-sor testing facility in Beihang University to accommodate the experiments.Firstly,the settling chamber,screen and other parts have been removed from this testing facility.In addition,the geometry of the compressor testing facility has been adjusted for this experiment.Modified compressor testing facility has been modeled using Duct-Compressor-Plenum model theory;cal-culations on estimating the effect of the systematic Helmholtz harmonic frequency have been con-ducted and investigated.Final results indicate that the settling chamber at the inlet cannot affect the systematic Helmholtz harmonic frequency,but can improve the uniformity of the flow and minimize the turbulence level.It can be concluded that the Duct-Compressor-Plenum model should not be applied to the testing facility when conducting experiments on it.